Calcination effects of 2D molybdenum disulfides

Highlights: • The thermal stability of native, commercial and hydrothermally grown 2D-MoS₂. • Molybdenum disulfide calcination in the synthetic air and Argon up to 1000 °C. • Mass spectrometry of emitted species from nanostructured MoS₂ Designing earth abundant, cost effective 2D-layered materials capable replace graphene and precious metal nanoparticulated arrays in optoelectronic and catalytically working devices are among global challenges. The key factor for these applications is thermostability of MoS₂ layered nanostructures. Herein, calcination effects of hydrothermally synthesized MoS₂ and commercial MoS₂ crystal as well as 1.7 and 6.0 μm-sized MoS₂ powders were studied in the synthetic air and argon gas environments by thermogravimetric and differential thermal analysis, mass spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy. Markedly lower thermal stability of hydrothermally synthesized 2D MoS₂ species both in the synthetic air and Ar environments compared to MoS₂ crystal and commercial powders have been established and transformations up to 1000 °C estimated. It was determined that oxidation of hydrothermally synthesized MoS₂ films in the synthetic air starts below 200 °C and results in a transformation of nanoplatelet-shaped films to MoO₃ sheets and nanowires at higher temperatures. The annealing in argon atmosphere, however, resulted in the MoS₂ crystallinity increase, S/Mo ratio reduction, and temperature-dependent transition of 3R-MoS₂ phase to 2H-MoS₂ no influencing markedly the morphology of nanoplatelets up to 520 °C.